CONCENTRATED, LIQUID, PERSONAL WASHING COMPOSITION COMPRISING ALKANE DIOLS

Abstract: A liquid bath foam composition comprising 30-60 wt.% of a surfactant system comprising a mixture of anionic and zwitteronic surfactants, 1-15 wt.% electrolyte and 9-20 wt.% of a 3 to 6 alkane diol solvent having no more than two hydroxy groups. The combined presence of electrolyte and specified diol type enable stable formulations to be prepared.

Description: CONCENTRATED, LIQUID, PERSONAL WASHING COMPOSITION COMPRISING A KANE DIOLS Technical Field The present invention relates to a personal washing composition having a high level of surfactant active which is particularly suitable for use as a bath foam. Background to the Invention Commercially available personal washing compositions, such as shower gels, facial cleansers, bath foams and hair shampoos, generally comprise 15-20%wt surfactant on product. Due to environmental concerns, and for reasons of economy, of packaging, storage, distribution and portability, it is desirable to produce more concentrated bath foam products, comprising 30-60%wt surfactant on product. EP 0288919 (Henkel 1987) discloses gel-form foam bath concentrates comprising as the bulk of the surfactant 35-45% wt of an alkyl ether sulphate and 5-15%wt polyglycol ether surfactants: i.e. at least 40% surfactant on product. The examples of this patent relate to formulations with around 60% surfactant and viscosities of around 12-24 Pa.s using a Haake Rotoviscomiter RV3 and MV2 cup and bob at a specified shear rate. At these higher surfactant concentrations, aqueous surfactant systems generally comprise a viscous-phase gel which disperses poorly, if at all, in water. Extremely poor dispersion can lead to excessive product wastage as the consumer tends to use excessive amounts of the product to obtain the desired results. Moreover viscous products are generally difficult to process, package and dispense. In view of the above, products should have a viscosity which is low enough for processing, packaging and dispensing. Products also need to be stable over a range of temperatures, homogeneous, preferably transparent, and comprise formulations which can suffer small variations in raw material properties without loss of stability and performance. Furthermore, products should be mild to the skin when used. Many mild, surfactants are known, however, these surfactants, unlike surfactants such as fatty acid soaps, are impractical to obtain in a relatively anhydrous form in commercial quantities, and are generally supplied as an admixture with water, typically as 30-40%w/w solutions of the product. The presence of such an excess water in the raw materials leads to formulation difficulties. As will be appreciated, this is particularly true where the desired concentration levels are above 30% surfactant on product. It is well known that organic solvents may be used in concentrated detergent compositions. In some cases these solvents are present in the composition to overcome solubility problems at high concentrations of active. However, while a wide range of solvents can be employed in general purpose cleaning compositions and other formulations not intended for application to, or prolonged contact with, the skin or hair, it will be appreciated that the presence of certain solvents at high levels is unacceptable where the composition is expected, in use, to contact the skin or hair of the user. For example, US patent 2607740 discloses a liquid detergent composition incorporating sulphated and sulphonated detergents (40-60wt%) and alkanolamides (10-20wt%) . In that document, the use of solvents is suggested in order to overcome solubility problems at high concentrations of active, the preferred solvent being a mixture of water and ethanol. US 4555360 relates to a detergent composition comprising anionic surfactant, betaine and a ine oxide (as a foam booster) plus 1-90% water and 3-10% lower molecular weight alcohol. In addition, US 4554098 relates to liquid detergents having reduced skin-irritation which include 30% alkyl ether sulphate, non-soap anionic, 1-8% zwitterionic surfactant (selected from betaine, amido- betaine and sulphobetaine) and an alcohol as a solubiliser. Alkanolamides, amine oxides and lower alkanols such as ethanol are undesirable in the present context due to potential problems of toxicity and flammability. Moreover, ethanol has an antifoaming action which makes it particularly unsuitable in the present application. As an alternative to alcohols, other solvents have been proposed for use in laundry and dishwashing detergents. US 4747977 discloses laundry detergent compositions which avoid the odour and safety problems associated with alcohols and include 33%wt anionic surfactant, l-15%wt nonionic surfactant and 4-25%wt of a polyol, preferably 1,2, propane diol (propylene glycol) or alternatively trimethylene glycol, diethylene glycol (2,2'oxy- bisethanol), hexylene glycol (2-methyl-2,4 pentandiol) or glycerine. The compositions of this disclosure comprise about 20%wt to about 70%wt water. EP 109022 relates to a concentrated liquid detergent comprising a mix of anionic and nonionic surfactants with solvents selected from alcohols, glycols, and ketones. US 4671894 discloses a liquid dishwashing detergent comprising 4-20% alkyl sulphate, 5-20% alkylbenzene sulphonate, 1-10% nonionic surfactant, 5-24% alkyl ethoxy sulphate, 0.25-10% zwitterionic surfactant (selected from alkylbetaine, alkyl-amidobetaine and sulphobetaine) and hydrotrope-water system in which the hydrotrope is selected from ethanol, urea, and/or lower alkyl benzene sulphonate. US 4088612 relates to compositions including sulphobetaines and anionic surfactant in molar ratio of not less than 1:2 in which lower alcohols are optional as hydrotropes. Hydrotropes are also known from EP 373851 which discloses a light duty liquid detergent including alkyl a idobetaines and alkyl amido-sulpho-betaines, 1-12% hydrotrope, optional electrolytes and an alkyl ether sulphate surfactant. The present invention provides a stable bath foam composition which contains a high level of active, electrolyte and a selected organic solvent (3-6 carbon alkane diol solvent having no more than 2 hydroxy groups) but has acceptable properties as regards viscosity and stability. Brief Description of the Invention A first aspect of the present invention provides a liquid, stable, concentrated bathfoa composition comprising: a) 30-60%wt of a surfactant system comprising a mixture of anionic and zwitterionic surfactants, b) l-15%wt electrolyte, and, c) 9-20%wt of a 3-6 carbon alkane diol solvent having no more than 2 hydroxy groups. Detailed Description of the Invention Without wishing to be bound by any theory of operation, it is believed, a synergistic interaction between the electrolyte and the selected alkane diol enables stable single phase formulations to be prepared. • Typically, no water need be added to these compositions to assist in the dispersion of the materials present, other than that which is present in the materials as supplied. Small quantities of water can however be added. Surfactants Both anionic and zwitterionic surfactants are essential components of the formulations according to the present invention. Preferably, the product comprises 30-45%wt of the anionic surfactant and l-15%wt of the zwitterionic surfactant. It is particularly preferred to employ 35-40% anionics and 4-10% zwitterionic. Typically, the formulations comprise, in total, at least 40% surfactant on product i.e. around 36%wt of anionic and around 9wt% zwitterionic. It is preferable that the anionic actives include one or more of fatty acid ether sulphates, alpha-olefin sulphonates, fatty isethionates, alkyl glyceryl ether sulphonates, mono-alkyl glyceryl sulphates, acyl sarcosinates, acyl taurides, alkyl and dialkyl sulphosuccinates, alkyl phosphates, and mixtures thereof. Preferred amongst the anionic surfactants are fatty acid ether sulphates, particularly lauryl ether sulphate salts such as sodium lauryl ether sulphate (SLES) . Alternative, preferred anionic surfactants include alkyl sulphosuccinate and fatty isethionates. These surfactants are preferred due to their mildness on human skin. As mentioned above, sodium lauryl ether sulphate (SLES) is particularly preferred as the anionic surfactant. SLES is a mixture of compounds having a mean chain length of from c ιo ~ c i 4 generally around C 12 and is commercially available in a concentrated form. It is preferable that the zwitterionic surfactant include one or more of betaines, amido betaines and sulpho betaines, and mixtures thereof. Coco-amidopropyl betaines are particularly preferred due to their low potential nitrosamine-precursor content and mildness properties. Electrolytes At least one electrolyte is an essential component of the formulations according to the present invention. A wide range of electrolytes are suitable. Preferred electrolytes are selected from the group comprising alkali metal or ammonium halides, particularly chlorides. The ratio of electrolyte to total surfactant is typically in the range 1:4-1:20. Electrolyte, is preferably present in a ratio to the surfactant of around 1:9 electrolyte:surfactant although the precise limits will vary with the type of surfactant used. Sodium chloride is the most preferred electrolyte, for reasons of cost and physiological acceptability. Diols It is essential that the compositions according to the present invention comprise at least one 3-6 carbon alkane diol solvent having no more than 2 hydroxy groups. Suitable diols within the scope of the present invention are 1,2-propane diol, 1,4-butanediol, 2,3-butanediol, 2- methyl-2,4 pentanediol, 2,2'oxy-bisethanol, 1,2-pentane diol. The most preferred of these solvents is 1,2-propane diol. This has preferred odour and volatility properties. Minors Minor components are inessential but typical components of personal washing compositions. These can be selected from one or more of opacifiers, preferably 0.2-2.0%wt; preservatives and perfumes, preferably 0.5-5%wt. In addition to the above, compositions according to the present invention can comprise a non-hydrotrope polyol, preferably glycerol . Examples of preservatives include: benzoic acid, sodium benzoate, sorbic acid, potassium sorbate, sodium propionate and the methyl, ethyl, propyl and butyl esters of p-hydroxybenzoic acid 2-bromo-2-nitropropane-l, 3-diol, phenoxyethanol, dibromo-dicyanobutane, formalin and Tricolsan. The amount of chemical preservative optionally to be incorporated in the composition according to the invention will generally be from 0.05 to 5%, preferably from 0.01 to 2% by weight, the amount chosen being sufficient to arrest microbial proliferation. Optional further components include colouring agents, germicides and anti-oxidants. Typical embodiments of the present invention provide a bath foam composition comprising: a) 30-45%wt alkyl ether sulphate, b) l-15%wt coco a ido propyl betaine, c) 9-20%wt 1,2-propane diol, d) l-15%wt electrolyte, and e) less than 50%wt water on product, said composition being free of added water. In order that the present invention may be further understood it will be illustrated hereafter by reference to the following non-limiting examples. EXAMPLES In the following examples the materials used are as listed below, all percentages are by weight: SLES: GENAPOL ZRO (RTM ex. Hoechst) sodium lauryl ether sulphate, average 3EO, 70% paste; anionic surfactant. CAPB: REWOTERIC AMB14 (RTM ex. REWO) coco-a ido propyl betaine, 30% aqueous solution: amphoteric surfactant, used as a co-active. NaCl Sodium chloride: electrolyte. SOLV: 1,2 propan-diol: ex BDH. PERF: Commercially available perfume. PRES: Preservative (formalin) EXAMPLES 1-8 and 9-28 Compositions were prepared as given in Tables 1 and 2 below, by mixing of the ingredients as specified, other than the SLES, in an aqueous mixture at room temperature and final addition of the SLES as a 70% paste, as supplied, also at room temperature. All additions were made under mild shear. All quantities are given in absolute terms accounting for water present in the raw materials, but not accounting for other impurities except as mentioned below. Comparative examples are given in Table 2a and 2b. TABLE 1 All of the products given in Table 1 were single-phase, stable, transparent, pourable, high foaming products suitable for use as bath foams. TABLE 2a 10 15 20 TABLE 2b The examples given in Tables 2a and 2b had one or more unacceptable properties selected from instability, dilution thickening, high solvent requirements or high- viscosity. Examples 9-13 exhibited a dispersed lamellar phase and were either non-transparent and had a tendency to cream, i.e. phase separation of the products would occur on storage. Examples 14-16 were unstable and phase-separated into a liquid phase and a solid component which precipitated out of the product. The solid component was believed to consist mostly of NaCl. o Examples 17-19 were highly viscous products which were difficult to manufacture and dispense. It is noted that in Example 17 a product could be made with acceptable stability but high levels of solvent were required. Example 20 comprised a highly viscous dispersed gel phase and was therefore unsuitable for use. Examples 21-22 illustrate that products can be formed without salt, but in the absence of the synergistic interaction between the salt and the solvent it was necessary to add unacceptably high levels of expensive solvent to obtain acceptable rheology. Example 23 comprised a highly viscous gel which was believed to be a hexagonal phase system. This was unpourable and quite unsuitable for use. Examples 24-28 illustrate that while less viscous products than that of example 23 can be formed without solvent, the absence of the synergistic interaction between the salt and the solvent leads to lamellar phase products which are pourable but exhibit highly pronounced dilution thickening on addition to bath water. This thickening behaviour severely hinders dispersion of the compositions in water.

Claims: CLAIMS 1. A liquid, stable, concentrated bathfoam composition comprising: a) 30-60%wt of a surfactant system comprising a mixture of anionic and zwitterionic surfactants, b) l-15%wt electrolyte, and, c) 9-20%wt of a 3-6 carbon alkane diol solvent having no more than 2 hydroxy groups. 2. Composition according to claim 1 comprising no added water. 3. Composition according to claim 1 comprising 30-45%wt of anionic surfactant. 4. Composition according to claim 3 wherein the anionic surfactant is selected from fatty acid ether sulphate, alkyl sulphosuccinate, fatty isethionates and mixtures thereof. 5. Composition according to claim 1 comprising l-15%wt of zwitterionic surfactant. 6. Composition according to claim 5 wherein the zwitterionic surfactant is selected from betaines, amido betaines, sulpho betaines, and mixtures thereof. 7. Composition according to claim 1 wherein the ratio of electrolyte to total surfactant ranges from 1:4 to 1:20. 8. Composition according to claim 1 wherein the diol is selected from the group comprising 1,2-propane diol, 1,4-bu anediol, 2,3-but.anediol, 2-methyl-2,4 pentanediol, 2,2'oxy-bisethanol, 1,2-pentane diol and mixtures thereof. 9. Composition according to claim 1 further comprising a non-hydrotrope polyol. 10. Composition according to claim 1 comprising: a) 30-45%wt alkyl ether sulphate, b) l-15%wt coco amido propyl betaine, c) 9-20%wt 1,2-propane diol, d) l-15%wt electrolyte, and, e) less than 50%wt water on product, said composition being free of added water.

Inventors: MOULD ROY ARTHUR STEADMAN, SALMON TOM MATTHEW F, MOULD, ROY, ARTHUR, STEADMAN, SALMON, TOM, MATTHEW, F.
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1994
Main classification: A61K7
IPC codes: A61K8, A61Q19, C11D1, C11D3